One preferred application of the present invention is in circuit interrupting or breaking devices. As used herein, the expression "circuit breaker" encompasses any device which interrupts current in an electrical circuit. This expression is not intended to be limited to devices that perform additional functions, such as, for example, reclosing. The background of the invention is described below in connection with circuit breakers generally. However, it should be noted that, except where they are expressly so limited, the claims at the end of this specification are not intended to be limited to applications of the invention in a circuit breaker.
One use of a circuit breaker is in the distribution of three phase electrical energy. When a sensor or protective relay detects a fault or other system disturbance on the protected circuit, the circuit breaker operates to physically separate current-carrying contacts in each of the three phases by opening the circuit to prevent the continued flow of current. The major components of a circuit breaker include the interrupters, which function to open and close one or more sets of current carrying contacts housed therein; the circuit switching mechanism, which provides the energy necessary to open or close the contacts; the arcing control mechanism and interrupting media, which create an open condition in the protected circuit; one or more tanks for housing the interrupters; and the bushings, which carry the high voltage electrical energy from the protected circuit into and out of the tank(s). One preferred application of the present invention is in connection with a trip latch mechanism for a circuit switching device.
An example of a circuit breaker is depicted in FIG. 1. As shown, the circuit breaker assembly 1 includes three cylindrical metal tanks 3. The three cylindrical tanks 3 form a common tank assembly 4 which is preferably filled with an inert, electrically insulating gas (e.g., SF.sub.6). The tank assembly 4 is referred to as a "dead tank" in that it is at ground potential. Each tank 3 houses an interrupter (not shown). The interrupters are provided with terminals connected to respective spaced bushing insulators. The bushing insulators are shown as bushing insulators 5a and 6a for the first phase; 5b and 6b for the second phase; and 5c and 6c for the third phase. Associated with each pole or phase is a current transformer 7. The circuit switching mechanism, or "operating mechanism," for opening and closing the interrupter contacts is contained within an operating mechanism housing 9. The operating mechanism is mechanically coupled to each of the interrupters via a linkage 8.
When used in connection with a switching mechanism, a trip latch holds the switching mechanism (that is, one or more springs of the switching mechanism) in a charged state until the potential energy stored by the switching mechanism is needed to open the protected circuit. Typical prior art trip latch mechanisms are required to withstand high impacts associated with open-close-open operations. Such prior art trip latches are necessarily sophisticated and expensive. A goal of the present invention is to provide a relatively simple, reliable, and inexpensive trip latch mechanism for circuit interrupting and other devices that are not required to perform open-close-open (i.e., reclosing) operations. A further goal of the present invention is to provide a trip latch mechanism which quickly removes itself from the path of moving parts propelled into motion upon release of the latch.